Question

To expand a 4-bit parallel adder to an 8-bit parallel adder, we can
(A) use two 4-bit adders and connect the sum output of one to the input bit of the other
(B) use four 4-bit adders with no interconnections
(C) use two 4-bit adders with the carry output of one connected to the carry input of the other
(D) use eight 4-bit adders with no interconnections

• A. (A), (C) only
• B. (B), (D) only
• C. (A) only
• D. (C) only

Hint:

When expanding adders, ensure that the carry outputs are properly connected to the next adder to maintain the integrity of the operation.

Answer 1

The Correct Option is A

Step 1: Expanding a 4-bit adder.
To create an 8-bit adder from 4-bit adders, connect two 4-bit adders in series. The carry-out of the first 4-bit adder should be connected to the carry-in of the second 4-bit adder. This cascading configuration allows for the addition of 8-bit numbers.
Final Answer: \[\boxed{1. \text{(A), (C) only}}\]